EP0083143B1 - Process for producing premium coke - Google Patents

Process for producing premium coke Download PDF

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Publication number
EP0083143B1
EP0083143B1 EP82201675A EP82201675A EP0083143B1 EP 0083143 B1 EP0083143 B1 EP 0083143B1 EP 82201675 A EP82201675 A EP 82201675A EP 82201675 A EP82201675 A EP 82201675A EP 0083143 B1 EP0083143 B1 EP 0083143B1
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EP
European Patent Office
Prior art keywords
decant oil
coke
hydrotreated
pyrolysis tar
cte
Prior art date
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Expired
Application number
EP82201675A
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German (de)
English (en)
French (fr)
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EP0083143A2 (en
EP0083143A3 (en
Inventor
Arthur William Moore
Eric Marshall Dickinson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Union Carbide Corp
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Union Carbide Corp
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Publication date
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
    • C10B57/00—Other carbonising or coking processes; Features of destructive distillation processes in general
    • C10B57/04—Other carbonising or coking processes; Features of destructive distillation processes in general using charges of special composition
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
    • C10B55/00—Coking mineral oils, bitumen, tar, and the like or mixtures thereof with solid carbonaceous material

Definitions

  • the invention relates to premium coke suitable for use in the production of a graphite electrode, and particularly to a process for producing a premium coke from a blend of pyrolysis tar and hydrotreated decant oil.
  • Premium coke is well known in the art and is a commercial grade of coke having acicular, anisotropic microstructure.
  • the premium cokes are used in the production of electrode grade graphite. This use of premium cokes results in various requirements to be made of the cokes. Some of these requirements are pointed out herein.
  • a graphite electrode which will be used in the arc melting of steel or the like must possess a low value for the coefficient of thermal expansion (CTE) because of the severe thermal shocks which occur in such processes.
  • the premium coke used for producing the graphite electrode must be capable of imparting a low CTE to the electrode.
  • the process for producing a graphite electrode from a premium coke requires that the electrode be heated to a temperature in the range of from about 2000°C to about 3000°C in order to provide energy to convert the carbon in the coke to a graphite crystalline form and to volatilize impurities.
  • a carbon body made from premium coke is heated to a temperature in the range of from about 1000°C to about 2000°C, various sulfur-containing compounds present in the coke decompose and this could result in a rapid, irreversible expansion, of the carbon body. This phenomenon is termed "puffing". It is desirable to use a low sulfur containing precursor material for producing the premium coke in order to minimize or preferably eliminate problems due to "puffing".
  • premium cokes are made from low sulfur containing, aromatic, slowly reacting feedstocks such as decant oils from catalytic cracking and tars obtained from the thermal cracking of decant oils and gas oils.
  • pyrolysis tars are relatively inexpensive mixtures of aromatic compounds and have low amounts of sulfur.
  • pyrolysis tars are heavy by-products of the cracking process for producing ethylene.
  • Pyrolysis tars are known to be unsuitable for the commercial production of premium coke because this production is carried out by the delayed coking process and the highly reactive pyrolysis tars convert to coke in the coils of the delayed coker furnace. This results in clogging and short operating periods.
  • U.S. Patent No. 3,817,853 hydrotreats a pyrolysis tar in the presence of an inert diluent and obtains a feedstock which produces graphite electrodes having a CTE of about 1.6x 10- 6 per °C and higher. While this is an improvement, a CTE of about 0.5x 10- 6 per °C or less is needed for high quality graphite electrodes.
  • the examples in the patent teach the use of from about 12.2 to about 18.7 standard cubic meters of hydrogen per barrel of pyrolysis tar. This is a relatively high cost process.
  • U.S. Patent No. 4,213,846 hydrotreats pyrolysis tars, petroleum resids, and thermal tars by coking them with a hydrogen donor diluent produced by the catalytic hydrotreatmentof a coker gas oil fraction generated from the delayed coking of the blend.
  • the hydrotreated feed is an ecLVal blend with fresh feed. This process has several drawbacks.
  • the hydrotreated coker gas oil does not contribute to the yield of the process and the examples teach a maximum of 15% by weight pyrolysis tars.
  • the instant invention overcomes the drawbacks of the prior art and provides a process for the commercial production of a premium coke suitable for making high quality graphite electrodes.
  • the invention is a process for producing a premium coke for making a graphite electrode having a CTE less than about 0.5x10- 6 per °C. comprising the steps of forming a blend of a pyrolysis tar and a hydrotreated decant oil which includes from 50% to 75% by weight of the pyrolysis tar and from 50% to 25% by weight of the hydrotreated decant oil; and coking the blend by delayed coking, whereby the premium coke is formed.
  • the hydrotreated decant oil is produced by hydrotreating a decant oil until there is added from about 2 to about 4 hydrogen atoms per average molecule of the decant oil, more preferably from about 2 to about 3 hydrogen atoms.
  • Another preferred embodiment of the invention is a graphite electrode made from the premium coke of the invention.
  • a pyrolysis tar as used herein and according to the prior art is generally the heaviest by-product of olefins production by vapor-phase cracking of liquid hydrocarbons in the presence of steam at temperatures of from about 760°C to about 930°C at pressures from about 100 pa to about 200 pa. It is the fraction which boils above about 200°C.
  • a decant oil as used herein and according to the prior art is generally the highest boiling by-product of gasoline production by catalytic cracking after the removal of catalyst particles by settling. It generally boils at a temperature above about 300°C.
  • the pyrolysis tar used in the invention should have a sulfur content of less than about 1 % by weight and the decant oil used in the invention should have a sulfur content of less than about 2% by weight.
  • the hydrotreatment of the decant oil provides the additional incidental advantage of hydrodesulfurizing the decant oil so that the potential problem of puffing is reduced or eliminated even though the hydrotreatment is not carried out for that purpose.
  • the hydrotreatment of the decant oil can be carried out in accordance with the prior art by contacting the decant oil with hydrogen at an elevated temperature and high pressure in the presence of a suitable catalyst.
  • a gas oil-based pyrolysis tar A having the properties shown in Table 1 was blended with a hydrotreated decant oil A, having the properties shown in Table 2. Three blends were prepared with the amounts of pyrolysis tar A being 25%, 50%, and 75% by weight.
  • a bench scale delayed coking unit as shown in Fig. 1 was used to coke each of the blends as well as separate portions of the pyrolysis tar A and the hydrotreated decant oil A.
  • the coking unit of Fig. 1 operates as follows:
  • the Table 3 shows that the distillates and cracking gas yields reduced as the amount of pyrolysis tar increased.
  • the coke from each of the tests was used to produce graphite electrodes in accordance with conventional testing procedures.
  • the procedure used is generally as follows:
  • the rod was then converted into a graphite electrode.
  • the last graphitizing temperature is in the range of from about 2800°C to about 3000°C.
  • the value of the longitudinal CTE of each rod was measured in the temperature range of from 30°C to 100°C. Only longitudinal CTE is of interest hereir..
  • Table 4 shows the values of CTE for rods made from different blends.
  • the hydrotreated decant oil modifies the pyrolysis tar to allow good continuous delayed coking and to provide excellent values of the CTE for high proportions of pyrolysis tar.
  • the amount of hydrotreatment given to the decant oil will have an effect on the process. If the decant oil is saturated, then it will not act as a donor. The lower limit for hydrotreating the decant oil for various blends can be determined experimentally.
  • Example 1 shows that high coke yields are obtained for relatively low amounts of hydrogen. It is also advantageous economically to hydrotreat the decant oil rather than the pyrolysis tar.
  • Example 1 The tests carried out in the Example 1 were carried out with the hydrotreated decant oil A of Example 1, and a predominantly kerosene-based pyrolysis tar B, having properties as shown in Table 5.
  • Table 6 shows the yields for the different blends and Table 7 shows the values of longitudinal CTE measured for graphite electrodes made from the blends.
  • the measured CTE's of the graphite electrodes made from blends having 50% and 75% pyrolysis tar were lower than one would calculate based on the mixture of the two components, and one would not expect to obtain good quality graphite electrodes based on such calculations.
  • the hydrotreated decant oil A of the Example 1 and the pyrolysis tar B of the Example 2 were blended to run tests with the pyrolysis tar content 0%, 50%, 75%, and 100%.
  • the pilot plant delayed coker shown in Fig. 2 was used.
  • the operation of the pilot plant delayed coker is as follows:
  • Table 8 shows some of the operating parameters of the pilot plant delayed coker. A pressure of about 275 K Pa was maintained, the throughput ratio was held as close to 2.0 as possible, and the furnace temperature was in the range of from about 470°C to about 500°C. The higher temperature was used for less reactive feedstocks whereas the lower temperature was used for more reactive feedstocks.
  • Graphite electrodes were made from the cokes calcined at 1000°C and the value of the CTE of each was measured, as in the Example 1. The measured values are shown in Table 9.
  • Blends were prepared of a hydrotreated decant oil B having the properties shown in Table 10 and a naphtha-based pyrolysis tar C having the properties shown in Table 11.
  • Example 12 shows the measured values of the CTE for each of the graphite electrodes.
  • the values of the CTE for the blends were considerably less than one would expect based on the rule of mixtures.
  • a pyrolysis tar D having the properties shown in Table 13 and hydrotreated decant oil A were blended together for coking in the pilot plant delayed coker. Blends having 0%, 50%, 75%, and 100% pyrolysis tar were used.
  • Blends were made with pyrolysis tar D and decant oil C, having the properties shown in Table 15 to show the results of blends which are not in accordance with the invention.
  • the bench scale delayed coker of the Example 1 was used for blends of 0%, 50%, 75%, and 100% pyrolysis tar.
  • Table 17 shows some of the operating parameters.
  • the relatively high level of sulfur for the graphite electrode made from an equal blend would be expected to present puffing problems and would be regarded as unacceptable. This high amount of sulfur is due to the omission of the hydrotreatment which would reduce the sulfur content of the decant oil.
  • Graphite electrodes were made from the blends except of the blend containing 25% pyrolysis tar. Table 18 shows the measured values of CTE.
  • Example 6 The tests carried out in the Example 6 were repeated in a pilot plant delayed coker for blends containing 0%, 50%, and 100% pyrolysis tar D.
  • the decant oil C was hydrotreated until there was added about 2.5 hydrogen atoms per average molecule of decant oil.
  • a blend of 50% of this hydrotreated decant oil with 50% pyrolysis tar D was also coked in the pilot plant coker.
  • Table 19 shows operating parameters and coke yields. Results for the blend containing 50% hydrotreated decant oil are shown by 50.
  • Table 20 shows that cokes made from the blends containing untreated decant oil have CTE's in accordance with those calculated by the rule of mixtures, whereas coke from the blend containing 50% hydrotreated decant oil has a CTE substantially lower than that calculated from the rule of mixtures.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Coke Industry (AREA)
  • Carbon And Carbon Compounds (AREA)
EP82201675A 1981-12-29 1982-12-29 Process for producing premium coke Expired EP0083143B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US33552081A 1981-12-29 1981-12-29
US335520 1981-12-29

Publications (3)

Publication Number Publication Date
EP0083143A2 EP0083143A2 (en) 1983-07-06
EP0083143A3 EP0083143A3 (en) 1984-05-30
EP0083143B1 true EP0083143B1 (en) 1986-01-22

Family

ID=23312130

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82201675A Expired EP0083143B1 (en) 1981-12-29 1982-12-29 Process for producing premium coke

Country Status (5)

Country Link
EP (1) EP0083143B1 (enrdf_load_stackoverflow)
JP (1) JPS58118889A (enrdf_load_stackoverflow)
DE (1) DE3268721D1 (enrdf_load_stackoverflow)
ES (1) ES8405834A1 (enrdf_load_stackoverflow)
ZA (1) ZA829563B (enrdf_load_stackoverflow)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5840386A (ja) * 1981-06-30 1983-03-09 ユニオン・カ−バイド・コ−ポレ−シヨン 高硫黄デカントオイルから低硫黄高品位コ−クスを製造する方法
US4466883A (en) * 1983-06-27 1984-08-21 Atlantic Richfield Company Needle coke process and product
US4624775A (en) * 1984-10-22 1986-11-25 Union Carbide Corporation Process for the production of premium coke from pyrolysis tar
NZ217510A (en) * 1985-09-12 1989-09-27 Comalco Alu Process for producing high purity coke by flash pyrolysis-delayed coking method

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3817853A (en) * 1972-05-30 1974-06-18 Union Oil Co Coking of pyrolysis tars
JPS5519277B2 (enrdf_load_stackoverflow) * 1973-07-02 1980-05-24
JPS5039081A (enrdf_load_stackoverflow) * 1973-08-08 1975-04-10
JPS518642A (ja) * 1974-07-12 1976-01-23 Matsushita Electric Ind Co Ltd Judokanetsuchoriki
JPS5144103A (en) * 1974-09-25 1976-04-15 Maruzen Oil Co Ltd Sekyukookusuno seizoho
US4178229A (en) * 1978-05-22 1979-12-11 Conoco, Inc. Process for producing premium coke from vacuum residuum
US4213846A (en) * 1978-07-17 1980-07-22 Conoco, Inc. Delayed coking process with hydrotreated recycle

Also Published As

Publication number Publication date
ES518648A0 (es) 1984-06-16
EP0083143A2 (en) 1983-07-06
JPS58118889A (ja) 1983-07-15
ES8405834A1 (es) 1984-06-16
ZA829563B (en) 1983-10-26
JPS6346800B2 (enrdf_load_stackoverflow) 1988-09-19
EP0083143A3 (en) 1984-05-30
DE3268721D1 (en) 1986-03-06

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